Ink collection device for a servicing station

ABSTRACT

An ink collection device for a servicing station of a franking machine, said ink collection device comprising: an ink collection reservoir for receiving the ink ejected, during a servicing stage, by ink ejection nozzles of at least one print module; at least one drainage duct placed above the reservoir and opening out in register with said at least one print module while defining a gap between a top of the drainage duct and the print module; and, mounted across said at least one drainage duct and at a small predetermined distance from the top of the drainage duct, means for causing the fine ink droplets ejected by said ink ejection nozzles to coalesce to form a plurality of thicker ink drops, and for causing said ink drops to drip under gravity into said ink collection reservoir.

FIELD OF THE INVENTION

The present invention relates exclusively to the field of mail handlingand it relates more particularly to an ink collection device in apostage meter or franking machine for franking mailpieces using inkjetprinting technology.

PRIOR ART

It is well known that using an inkjet print head is affected byclogging-up of the ink ejection nozzles of the head.

Therefore, inkjet ejection nozzles need to be cleaned periodically andit is necessary to spit ink out during such cleaning so as not to leavedried ink in the nozzles. Since the lifespan of the print head of afranking machine can currently reach about 1.5 million cycles, suchperiodic spraying of ink represents a relatively large quantity ofresidual ink (typically, it is recommended to spit out 4000 droplets ateach cleaning cycle). In current machines, that quantity is accumulatedon a plane sponge disposed in a reservoir or “spittoon” mounted at theservicing station for servicing the print head.

Unfortunately, such a solution, as illustrated, for example, by PatentApplication US2003/0142150 is not without drawbacks. Firstly, due to thelarge volume of ink spat out in a limited time during the cleaningcycle, the sponge must be a relatively long way away from the inkejection nozzles, and this gives rise to ink-droplet aerosol phenomenathat then soil the servicing station and more generally the structure ofthe franking machine as a whole, in particular the various cells fordetecting presence of mailpieces. In addition, such aerosol phenomenaare worsened by the flow of air generated by the fan when thetemperature of the motor in the machine rises or by the movement of themailpieces after a cleaning cycle.

OBJECT AND DEFINITION OF THE INVENTION

The present invention proposes to mitigate those drawbacks with an inkcollection device for a servicing station of a franking machine, saidink collection device comprising:

-   -   an ink collection reservoir for receiving the ink ejected,        during a servicing stage, by ink ejection nozzles of at least        one print module; and    -   at least one drainage duct placed above the reservoir and        opening out in register with said at least one print module        while defining a gap between a top of said drainage duct and        said print module;    -   wherein said ink collection device further comprises at least        one smooth pin mounted across said at least one drainage duct,        being placed at a determined distance from said ink ejection        nozzles and aligned on said nozzles, said pin having a diameter        that is adapted to the diameter of said ink ejection nozzles and        to said determined distance, so as to cause the fine ink        droplets ejected by said ink ejection nozzles to coalesce to        form a plurality of thicker ink drops, and so as to cause said        ink drops to drip under gravity into said ink collection        reservoir.

Thus, the fine ink droplets ejected by the nozzles are collected, andrun off as thick drops before the aerosol phenomena occur as in theprior art. Ink sprays are avoided and there is no longer any soiling ofthe servicing station or of the franking machine, and in particular ofthe electronic circuits thereof and of the casing thereof.

Preferably, said determined distance between said ink ejection nozzlesand said smooth pin lies in the range 3 millimeters (mm) to 5 mm, andthe diameter of said smooth pin lies in the range 1 mm to 2 mm.

When said print module has two parallel rows of ink ejection nozzles,said drainage duct has two parallel pins that are united to form ahairpin-shape pin with two parallel open branches, the curved junctionportion between the two branches of said hairpin-shape pin being heldsecurely in said drainage duct by a fastener stud.

The present invention also provides a franking machine servicing stationincluding the above-mentioned ink collection reservoir.

BRIEF DESCRIPTION OF THE DRAWINGS

The characteristics and advantages of the present invention appear moreclearly from the following description given by way of non-limitingindication and with reference to the accompanying drawings, in which:

FIG. 1 is a diagrammatic view showing the improved ink collection deviceof the invention;

FIG. 1A shows a detail of FIG. 1;

FIG. 2 is a perspective view showing the drainage ducts of the device ofFIG. 1;

FIG. 3 is a perspective view of a prior art ink collection device; and

FIG. 4 is a view from below of a standard print module having two rowsof ink ejection nozzles, which module is implemented both in the priorart ink collection device and in the ink collection device of theinvention.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

FIG. 3 is a fragmentary diagrammatic view of a prior art ink collectiondevice implemented in a servicing station of a franking machineincluding two inkjet modules 12, 14 mounted side-by-side and offset intwo mutually perpendicular directions. As is known, when the printmodules are in the servicing position (i.e. set back from the operatingposition, shown in dashed lines, in the path along which the mailpiecesare conveyed), an ink collection reservoir 16 equipped with itsabsorbent foam or sponge 18 is disposed under said two inkjet printmodules. As shown in FIG. 4, each print module has two parallel rows ofink ejection nozzles 12A, 12B; 14A, 14B, each row typically comprising250 nozzles. In order to avoid it having to be changed too frequently,the reservoir presents a volume that is relatively large, and it musttherefore be placed some distance away from the ink ejection nozzles.Two drainage ducts 22, 24 are thus provided between the reservoir andthe two print modules, which ducts are placed above the reservoir andare in the form of wells of substantially rectangular shape, each ductbeing disposed vertically in register with a respective one of the twomodules and draining the ink from the ejection nozzles towards thesponge of the reservoir. The ejection nozzles are separated from thetops of said ducts merely by respective gaps 20 of in the range 1 mm to2 mm that suffice to enable the print modules to move. Naturally, theducts are of cross-section that is dimensioned to surround as closely aspossible the two rows of nozzles with which each print module isprovided.

During the periodic cleaning of the print modules, the ejection nozzlesof those modules spit ink out and thus spray ink through the drainageducts to the reservoir that faces them. Ink is also spat out when themachine is switched on, and after it has been put on standby for aprolonged period of time. However, although such spraying is, in theory,directed due to the action of the drainage ducts, it is impossible toavoid aerosol phenomena that take advantage of the gap 20 and quicklylead to the servicing station and the various elements of thesurrounding franking machine being soiled. In practice, with onecleaning cycle every 300 printing operations, the inventors haveobserved that it takes only 30,000 print operations for the servicingstation to be totally soiled.

That is why, in accordance to the invention, and as shown in FIGS. 1 and1A, provision is made to place a smooth pin 26, 28 at a smallpredetermined distance, typically no more than 5 mm, from each row ofink injection nozzles, which pin is aligned along the row and placedacross each well that is placed above the ink collection reservoir 16and that opens out into said reservoir. For this purpose, each well isprovided with openings 22A, 22B, 22C, 22D; 24A, 24B, 24C, 24D in twoopposite faces. When each print module has two parallel rows, as shown,the two pins can be united in the manner of a hairpin-shape pin havingtwo open branches 26 a, 26B; 28A, 28B. Said hairpin-shape pin is heldsecurely at the curved junction portion between its two branches by afastener stud 22E, 24E extending from the outside face of each duct. Thesmall gap existing between the ejection nozzles and the pins makes itpossible to collect the ink before aerosol phenomena occur as in theprior art. Once they have been ejected, the fine ink droplets flattenout on the pins, and coalesce to from thicker ink drops that run offaround the pins and ultimately drip under gravity directly into thereservoir, or trickle down along their respective ducts. The entirelysmooth surface of the pin allows the ink to run off quickly and preventsdroplets from piling up on top of the pin, and its small diameter doesnot give rise to any delay in the formation of the ink drops.

More particularly, the diameter of the pin is adapted to the diameter ofthe nozzles and to the distance between the nozzles and the pin. If thediameter of the pin is too small or if the pin is too far away from thenozzles, the dispersion of the droplets is not braked. If said diameteris too large, the formation of droplets is disrupted and, when the printmodule has two rows of nozzles, a bridge of ink forms between the twopins that are placed below respective ones of the two rows and that arethen too close together.

In practice, for nozzle diameters of 0.04 mm and a pitch of 4.11 mm fromrow to row, each of which has a length of 12.66 mm, the inventors haveobtained excellent results with a pin having a diameter of 1.5 mm andplaced at a distance of 3.8 mm from the nozzles. For a distance betweenthe nozzles and the pin lying in the range 3 mm to 5 mm and a nozzlediameter lying in the range 0.02 mm to 0.05 mm, a pin diameter lying inthe range 1 mm to 2 mm is entirely satisfactory.

Thus, with the invention, by collecting ink drops as close as possibleto the ejection nozzles, soiling of the servicing station and thus ofthe franking machine is delayed considerably, given that tests performedby the inventors show that even after 1.5 million print cycles, nosignificant soiling is observed, including on the casing of the frankingmachine.

1. An ink collection device for a servicing station of a frankingmachine, said ink collection device comprising: an ink collectionreservoir for receiving the ink ejected, during a servicing stage, byink ejection nozzles of at least one print module; and at least onedrainage duct placed above the reservoir and opening out in registerwith said at least one print module while defining a gap between a topof said drainage duct and said print module; wherein said ink collectiondevice further comprises at least one smooth pin mounted across said atleast one drainage duct, being placed at a determined distance from saidink ejection nozzles and aligned on said nozzles, said pin having adiameter that is adapted to the diameter of said ink ejection nozzlesand to said determined distance, so as to cause the fine ink dropletsejected by said ink ejection nozzles to coalesce to form a plurality ofthicker ink drops, and so as to cause said ink drops to drip undergravity into said ink collection reservoir.
 2. An ink collection deviceaccording to claim 1, wherein said determined distance between said inkejection nozzles and said smooth pin lies in the range 3 mm to 5 mm, andthe diameter of said smooth pin lies in the range 1 mm to 2 mm.
 3. Anink collection device according to claim 1, wherein, when said printmodule has two parallel rows of ink ejection nozzles, said drainage ducthas two parallel pins that are united to form a hairpin-shape pin withtwo parallel open branches, the curved junction portion between the twobranches of said hairpin-shape pin being held securely in said drainageduct by a fastener stud.
 4. A franking machine servicing stationincluding an ink collection device according to claim 1.